sort_order = ['Adventure', 'Musical', 'Comedy', 'Romantic Comedy', 'Action',
'Drama', 'Concert/Performance', 'Documentary', 'Western',
'Thriller/Suspense', 'Horror', 'Black Comedy']
alt.Chart(movies_extended).mark_bar().encode(
alt.X('count()', stack='normalize', title='Proportion of movies'),
alt.Y('Major Genre', sort=sort_order),
alt.Color('MPAA Rating'),
alt.Order('MPAA Rating'))